Is this normal?

I'm 18 weeks along. At the beginning of my pregnancy I had bad period like cramps every day which doctor said was normal. They went away the beginning of my second trimester. Now the past two weeks or so I will randomly get REALLY intense painful cramps in my lower abdomen that last maybe a couple minutes or so sometimes a little longer but then they go away. Other then that I feel pretty good and so far at my doctors appointments everything has looked good. Anyone else have this? This is my fiat so I don't know what contractions feel like or if they can even happen this early. I have my 20 week appointment in two weeks.